The multi-enzyme complex, tryptophan synthase from Salmonella typhimurium, has been further analyzed by X-ray diffraction. High resolution data have been collected for two derivatives of a mutant, K87T, of the beta subunit that approximate enzyme catalyzed intermediates. These structures have been refined, to provide new information about the disposition of residues and their interaction with the intermediates of the beta reaction. In addition another mutant, alpha60E, has been analyzed and data have been collected for two inhibitor complexes of the betaK87T mutant to examine the effect on flexible regions of the alpha active site.